Am I missing something or did Anderson make a big mess up in the time line when writing Afterlife?? According to the previous movies&my math at the begining of the movie when it says "four years later" it should be SIX!!???

Alice makes it clear upon meeting up w/ clair again its been a year and half sence getting the chopper in the desert. And when finding clair in alaska its six months after the attack on the japan facility.so from this you can see it took alice and her clones a year to reach japan. If you do the math w/ the first three films you know its been 5years allready at the end of extinction.add a year and you got SIX!!!!??